1. Field of the Invention
The present invention relates to a water dispersible flame retardant composition including graphite functionalized with phosphoric acid and a method for preparing the same.
2. Description of the Related Art
In recent years, resin compositions or coating compositions using flame retardants have received attention due to their ability to protect property and save lives from fires. General polymeric materials such as resins and coatings composed of organic polymers are susceptible to heat. The polymer chains of such polymeric materials are liable to be decomposed in the presence of an ignition source and finally the polymeric materials are burnt while releasing large amounts of flammable gases. In comparison with natural polymeric materials, most synthetic polymers are decomposed to produce very toxic gases, posing an increased danger to people in case of fire.
For the purpose of avoiding this danger, excess inorganic materials (e.g., calcium carbonate) are compounded with resin compositions or coating compositions. In this case, however, the inorganic materials deteriorate the physical properties of the compositions in terms of tensile force and elongation, making it difficult to expect good workability. Further, desired heat resistance is difficult to attain when the inorganic materials are mixed in amounts that are workable. Some flame retardants focus on the functions of preventing the heat of combustion and blocking supply of oxygen from the outside to prevent or minimize the propagation of combustion from fires. Such flame retardants include metal hydrate inorganic flame retardants containing metals, halogenated flame retardants, phosphorus-based flame retardants containing phosphoric acid or phosphate, and nitrogen-based flame retardants containing nitrogen atoms. Based on the total amount of flame retardants that are currently in use, inorganic flame retardants are most widely used and halogenated flame retardants follow.
However, toxic gases are produced by incomplete burning of halogens. Water tends to react with halogens. Due to these disadvantages, the use of halogenated flame retardant decrease gradually. For this reason, non-halogenated flame retardants are getting attention with the recent increasing demand. Under such circumstances, phosphorus-based flame retardants are receiving particular interest, and as a result, a steep rise in the price of phosphorus-based flame retardants leads to shortage of supply. Further, since the performance of phosphorus-based flame retardants is still inferior to that of halogenated flame retardants, much research aimed at commercialization of phosphorus-based flame retardant remains to be done.
Japanese Patent Publication No. Hei 6-24723 discloses a flame retardant wallpaper including a flame-retardant, flexible graphite composite and a method for producing the same. Japanese Patent Publication No. Hei 10-101316 discloses a flame retardant composition including a composite of ammonium polyphosphate and graphite. In the flame retardant composition, the use of a strong acid is required to disperse the graphite and the amount of the graphite added is limited.
Korean Patent Application No. 2008-0048680 discloses a volume expandable nontoxic flame retardant resin composition including a polypropylene resin, graphite, red phosphorus, magnesium hydroxide, an ethylene propylene rubber, and a Teflon resin. The composition is merely to obtain a combination of the volume expandability of graphite and the flame retardant effect of red phosphorus. The patent application does not suggest a solution to improve the dispersibility of graphite.